Radio frequency plasma modified lithium-rich manganese oxide positive electrode material and preparation method and application thereof

Abstract

The invention discloses a radio frequency plasma modified lithium-rich manganese oxide positive electrode material as well as a preparation method and application thereof, and relates to the technical field of lithium ion battery positive electrode materials. The method comprises the following steps: mixing lithium acetate dihydrate, nickel acetate tetrahydrate, cobalt acetate tetrahydrate, manganese acetate tetrahydrate and citric acid monohydrate, adding into deionized water, and stirring; and carrying out spray drying, heat treatment and radio frequency plasma treatment to prepare the radio frequency plasma modified lithium-rich manganese oxide positive electrode material. According to the method, other chemical reagents do not need to be added, the lithium-rich manganese material is modified by changing the discharge time of the radio frequency plasma, nitrogen-nitrogen triple bonds can be broken due to the high energy density of the radio frequency plasma, the whole discharge area is more uniform, the interlayer spacing of the obtained modified lithium-rich manganese material is increased, the surface oxygen vacancy content is increased, and the performance of the material is improved. Therefore, the lithium ion battery has excellent cycle performance under high current density. The invention solves the problem of complex modification process of the existing lithium-rich manganese-based positive electrode material.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion battery positive electrode material preparation, and in particular to a radio frequency plasma modified lithium-rich manganese oxide positive electrode material and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries have been widely used in electric vehicles and hybrid vehicles due to their high power density and high energy density. Among the positive electrode materials of lithium-ion batteries, lithium-rich manganese layered materials Li2MnO3·LiMO2 (M=Mn, Ni, Co, Fe, Cr, etc.) have high specific capacity (up to 250mA hg -1 ), low cost and high safety, however, their electrode kinetics are poor, resulting in poor rate performance and poor cycling stability, and the kinetics may become even worse for lithium-rich materials with large and dense particles. In recent years, a lot of efforts have been made to stabilize the structure and improve the kinetics, and modification methods such as doping, heterostructures and coatings have been used to overcome these problems that plague their practical implementation.

[0003] In the patent with publication number CN117756194A, a modified lithium-rich manganese-based positive electrode material and its preparation method and application are disclosed. The doped manganese dioxide is prepared by pre-preparing a doped Mn-MOF, which can ensure that the doped elements can be accurately doped into the target position. The bulk doped elements can stabilize the adjacent Mn-O, Co-O and Ni-O bonds, and improve the migration energy barrier of Mn, Co, and Ni, thereby greatly improving the structural stability of the lithium-rich positive electrode material. In the patent with publication number CN117446875A, a modified lithium-rich manganese-based positive electrode material and its preparation method and application are disclosed. By setting a manganese hydroxide coating layer on the surface of the lithium-rich manganese-based precursor and then sintering at a low temperature to obtain a spinel phase structure, the high specific surface area of ​​the lithium-rich manganese-based positive electrode material can be ensured while improving the structural stability of the material. The spinel phase manganese oxide can prevent the performance of the material from deteriorating during the charge and discharge process. Among the many modification methods, foreign atoms or other chemical reagents are introduced to reconstruct the lithium-rich manganese surface, which will lead to the defect of complex and cumbersome process and difficult large-scale commercial application. Summary of the invention

[0004] In order to solve the above technical problems, the purpose of the present invention is to provide a radio frequency plasma modified lithium-rich manganese oxide positive electrode material and a preparation method and application thereof, so as to solve the problem of complex modification process of existing lithium-rich manganese-based positive electrode materials.

[0005] The technical solution of the present invention to solve the above technical problems is as follows: a method for preparing a radio frequency plasma modified lithium-rich manganese oxide positive electrode material is provided, comprising the following steps:

[0006] (1) lithium acetate dihydrate, nickel acetate tetrahydrate, cobalt acetate tetrahydrate, manganese acetate tetrahydrate and citric acid monohydrate are mixed, added into deionized water, and stirred to prepare a precursor solution;

[0007] (2) spray drying the precursor solution obtained in step (1), and then heat treating it to obtain a lithium-rich manganese oxide positive electrode material;

[0008] (3) subjecting the lithium-rich manganese oxide positive electrode material obtained in step (2) to radio frequency plasma treatment to obtain a radio frequency plasma modified lithium-rich manganese oxide positive electrode material.

[0009] The beneficial effects of the present invention are as follows: the lithium-rich manganese-based positive electrode material treated by radio frequency plasma of the present invention has a high specific capacity and excellent cycle performance at a high current density. Under certain conditions of discharge atmosphere and discharge power, a lithium-rich manganese material with oxygen vacancy defects can be obtained by changing the discharge time.

[0010] On the basis of the above technical solution, the present invention can also be improved as follows:

[0011] Furthermore, in step (1), the molar ratio of lithium acetate dihydrate, nickel acetate tetrahydrate, cobalt acetate tetrahydrate and manganese acetate tetrahydrate is 1.1-1.3:0.13-0.135:0.17-0.175:0.49-0.495.

[0012] Furthermore, in step (1), the molar ratio of lithium acetate dihydrate, nickel acetate tetrahydrate, cobalt acetate tetrahydrate and manganese acetate tetrahydrate is 1.1-1.3:0.13-0.135:0.17-0.175:0.49-0.495, and lithium acetate dihydrate is additionally added in an amount of 3% by mole of the original lithium acetate dihydrate to compensate for the lithium loss during the heat treatment process.

[0013] Furthermore, in step (1), the molar ratio of lithium acetate dihydrate, nickel acetate tetrahydrate, cobalt acetate tetrahydrate and manganese acetate tetrahydrate is 1.2:0.132:0.172:0.492.

[0014] Furthermore, in step (1), the molar ratio of lithium acetate dihydrate, nickel acetate tetrahydrate, cobalt acetate tetrahydrate and manganese acetate tetrahydrate is 1.2:0.132:0.172:0.492, and lithium acetate dihydrate is additionally added in an amount of 3% by mole of the original lithium acetate dihydrate to compensate for the lithium loss during the heat treatment process.

[0015] Furthermore, the total concentration of metal acetate in the precursor solution is 0.13-0.18 mol / L, and the concentration of citric acid monohydrate is 0.25-0.35 mol / L.

[0016] Furthermore, in step (1), the total concentration of metal acetate in the precursor solution is 0.15 mol / L, and the concentration of citric acid monohydrate is 0.3 mol / L.

[0017] Furthermore, in step (1), stirring is performed at 20-30° C. for 1-2 h.

[0018] Furthermore, in step (1), stirring is carried out at 25° C. for 1 h.

[0019] Furthermore, in step (1), the stirring speed is 450-550 rpm.

[0020] Furthermore, in step (1), the stirring speed is 500 rpm.

[0021] Furthermore, in step (2), the inlet temperature of the spray drying is 200-250°C, the outlet temperature is 110-115°C, and the feed rate is 1-2 L / h.

[0022] Furthermore, in step (2), the inlet temperature of the spray drying is 230° C., the outlet temperature is 115° C., and the feed rate is 1 L / h.

[0023] Furthermore, in step (2), the temperature is raised to 900-1200° C. at a heating rate of 2-4° C. / min in an air atmosphere and kept at this temperature for 18-22 minutes to complete the heat treatment process.

[0024] Furthermore, in step (2), the temperature is raised to 1000° C. at a heating rate of 3° C. / min in an air atmosphere and kept at that temperature for 20 min to complete the heat treatment process.

[0025] Furthermore, in step (3), nitrogen is used for radio frequency plasma treatment.

[0026] Furthermore, the radio frequency plasma treatment power is 200W, and the time is 1-30min.

[0027] Furthermore, in step (3), the lithium-rich manganese oxide positive electrode material obtained in step (2) is placed in a radio frequency plasma treatment device, the quartz tube is evacuated to a vacuum degree of 0.1 Pa, nitrogen is introduced, and then the gas flow rate is increased and the gas pressure in the quartz tube is ensured to be stable. After ventilation for 10 minutes, the radio frequency automatic matcher and the radio frequency power supply are turned on to perform radio frequency plasma treatment.

[0028] The present invention also provides a radio frequency plasma modified lithium-rich manganese oxide positive electrode material prepared by the method.

[0029] Furthermore, the chemical formula of the RF plasma modified lithium-rich manganese oxide cathode material is Li 1.2 Ni 0.132 Co 0.172Mn 0.492 O2.

[0030] The present invention also provides the use of the radio frequency plasma modified lithium-rich manganese oxide positive electrode material in the preparation of lithium ion batteries.

[0031] The present invention has the following beneficial effects:

[0032] 1. No need to add other chemical reagents, the lithium-rich manganese material can be modified by changing the radio frequency plasma discharge time. Nitrogen is an inert gas, and the nitrogen-nitrogen triple bond has a strong bond energy. Due to its high energy density, radio frequency plasma can break the nitrogen-nitrogen triple bond and make the entire discharge area more uniform. The interlayer spacing of the modified lithium-rich manganese material is increased, and the surface oxygen vacancy content is increased, so that it has excellent cycle performance at high current density. In addition, the surface electronic structure of the lithium-rich manganese material is also adjusted, so that the Mn valence state is increased and the Ni valence state is reduced, stabilizing the material structure while having high capacity.

[0033] 2. The preparation method of the lithium-rich manganese-based positive electrode material provided by the present invention has a simple synthesis process and low material cost. The modification method is green and efficient, and a lithium-rich manganese-based positive electrode material with excellent electrochemical performance can be obtained by changing the discharge time of the radio frequency plasma.

[0034] 3. The modified lithium-rich manganese oxide positive electrode material of the present invention changes the discharge time by 20min and 30min in N2 discharge atmosphere, the (003) peak shifts to a low angle, the interlayer spacing increases, and the oxygen vacancy content is 30.47% and 34.64%, respectively, which are higher than the oxygen vacancy content (27.76%) of the unmodified lithium-rich manganese material. The lithium-ion battery assembled with the LRO / N2-30min sample prepared by the method of the present invention has an initial discharge specific capacity of 271.89mAh / g at a current density of 20mA / g; after 325 cycles at a current density of 200mA / g, the capacity retention rate reaches 70%; at a current density of up to 1000mA / g, it has a high capacity of 169.28mAh / g, and after 285 cycles, the capacity retention rate is as high as 70%. The lithium-rich manganese oxide positive electrode material modified by radio frequency plasma in the present invention has electrochemical properties superior to most lithium-rich manganese-based positive electrode materials, and improves the performance and effect of lithium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 XRD diagrams of the positive electrode materials obtained in Examples 1-2 and Comparative Example 1;

[0036] Figure 2 The SEM images of the positive electrode materials obtained in Examples 1-2 and Comparative Example 1;

[0037] Figure 3XPS O1s graphs of the positive electrode materials obtained in Examples 1-2 and Comparative Example 1;

[0038] Figure 4 XPS Mn2p diagram of the positive electrode materials obtained in Examples 1-2 and Comparative Example 1;

[0039] Figure 5 XPS Ni2p diagram of the positive electrode materials obtained in Examples 1-2 and Comparative Example 1;

[0040] Figure 6 The first charge and discharge diagram of the positive electrode materials prepared in Examples 1-2 and Comparative Example 1;

[0041] Figure 7 The cycle performance of the positive electrode materials prepared for Examples 1-2 and Comparative Example 1 at a current density of 200 mA / g;

[0042] Figure 8 The rate performance diagram of the positive electrode materials prepared in Examples 1-2 and Comparative Example 1;

[0043] Fig. 9 The cycle performance of the positive electrode materials prepared for Examples 1-2 and Comparative Example 1 at a current density of 1000 mA / g. DETAILED DESCRIPTION

[0044] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples are only used to explain the present invention and are not used to limit the scope of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0045] Embodiment 1:

[0046] A radio frequency plasma modified lithium-rich manganese oxide positive electrode material, the chemical formula of which is: Li 1.2 Ni 0.132 Co 0.172 Mn 0.492 O2, the preparation method thereof comprises the following steps:

[0047] (1) lithium acetate dihydrate, nickel acetate tetrahydrate, cobalt acetate tetrahydrate, manganese acetate tetrahydrate and citric acid monohydrate were mixed, added into deionized water, and stirred at 500 rpm for 1 h at 25° C. to prepare a precursor solution;

[0048] The molar ratio of lithium acetate dihydrate, nickel acetate tetrahydrate, cobalt acetate tetrahydrate and manganese acetate tetrahydrate is 1.2:0.132:0.172:0.492; lithium acetate dihydrate is additionally added in an amount of 3% of the original lithium acetate dihydrate to compensate for the lithium loss during the heat treatment process; the total concentration of metal acetate in the precursor solution is 0.15 mol / L, and the concentration of citric acid monohydrate is 0.3 mol / L;

[0049] (2) The precursor solution obtained in step (1) is sent to a spray dryer by a peristaltic pump, and spray dried at high temperature and high pressure, wherein the inlet temperature of the spray dryer is 230° C., the outlet temperature is 115° C., and the feed rate is 1 L / h; then placed in an alumina crucible (120 mm, 120 mm in width, and 50 mm in height), and the alumina crucible is placed in a box furnace, and heated to 1000° C. at a heating rate of 3° C. / min in an air atmosphere, and kept warm for 20 min to complete the heat treatment process, thereby obtaining a lithium-rich manganese oxide positive electrode material;

[0050] (3) The lithium-rich manganese oxide positive electrode material obtained in step (2) is placed in a low-pressure radio frequency plasma treatment device, the quartz tube is evacuated to a vacuum degree of 0.1 Pa, nitrogen is slowly introduced, and then the gas flow rate is slowly increased to ensure that the gas pressure in the quartz tube is stable. After ventilation for 10 minutes, the radio frequency automatic matching device and the radio frequency power supply are turned on, the power is maintained at 200 W, the discharge time is 20 minutes, and radio frequency plasma treatment is performed to obtain a radio frequency plasma modified lithium-rich manganese oxide positive electrode material (named LRO / N2-20min).

[0051] Embodiment 2:

[0052] A radio frequency plasma modified lithium-rich manganese oxide positive electrode material, the chemical formula of which is: Li 1.2 Ni 0.132 Co 0.172 Mn 0.492 O2, the preparation method thereof comprises the following steps:

[0053] In step (3), the discharge time is 30 minutes, and radio frequency plasma treatment is performed to obtain radio frequency plasma modified lithium-rich manganese oxide positive electrode material (named LRO / N2-30 min). The rest is the same as in Example 1.

[0054] Embodiment 3:

[0055] A radio frequency plasma modified lithium-rich manganese oxide positive electrode material, the chemical formula of which is: Li 1.2 Ni 0.132 Co 0.172 Mn 0.492 O2, the preparation method thereof comprises the following steps:

[0056] (1) lithium acetate dihydrate, nickel acetate tetrahydrate, cobalt acetate tetrahydrate, manganese acetate tetrahydrate and citric acid monohydrate were mixed, added into deionized water, and lithium acetate dihydrate with a mass fraction of 3% was additionally added to compensate for lithium loss during heat treatment, and stirred at 450 rpm for 2 h at 20° C. to prepare a precursor solution;

[0057] The molar ratio of lithium acetate dihydrate, nickel acetate tetrahydrate, cobalt acetate tetrahydrate and manganese acetate tetrahydrate is 1.1:0.13:0.17:0.49; and lithium acetate dihydrate is additionally added in an amount of 3% of the original lithium acetate dihydrate to compensate for the lithium loss during the heat treatment process; the total concentration of metal acetate in the precursor solution is 0.13 mol / L, and the concentration of citric acid monohydrate is 0.25 mol / L;

[0058] (2) The precursor solution obtained in step (1) is sent to a spray dryer by a peristaltic pump, and spray dried at high temperature and high pressure, wherein the inlet temperature of the spray dryer is 200° C., the outlet temperature is 110° C., and the feed rate is 1.5 L / h; then placed in an alumina crucible (120 mm, 120 mm in width, and 50 mm in height), and the alumina crucible is placed in a box furnace, and heated to 900° C. at a heating rate of 2° C. / min in an air atmosphere, and kept warm for 22 min to complete the heat treatment process, thereby obtaining a lithium-rich manganese oxide positive electrode material;

[0059] (3) placing the lithium-rich manganese oxide positive electrode material obtained in step (2) in a low-pressure radio frequency plasma treatment device, evacuating the quartz tube to a vacuum degree of 0.1 Pa, slowly introducing nitrogen, then slowly increasing the gas flow rate, and ensuring that the air pressure in the quartz tube is stable. After ventilation for 20 minutes, turn on the radio frequency automatic matching device and the radio frequency power supply, maintain a power of 200 W, and discharge for 1 minute to perform radio frequency plasma treatment to obtain a radio frequency plasma modified lithium-rich manganese oxide positive electrode material.

[0060] Embodiment 4:

[0061] A radio frequency plasma modified lithium-rich manganese oxide positive electrode material, the chemical formula of which is: Li 1.2 Ni 0.132 Co 0.172 Mn 0.492 O2, the preparation method thereof comprises the following steps:

[0062] (1) lithium acetate dihydrate, nickel acetate tetrahydrate, cobalt acetate tetrahydrate, manganese acetate tetrahydrate and citric acid monohydrate were mixed, added into deionized water, and lithium acetate dihydrate in an amount of 3% by mole of the original lithium acetate dihydrate was additionally added to compensate for lithium loss during heat treatment, and stirred at 550 rpm for 1.5 h at 30° C. to prepare a precursor solution;

[0063] The molar ratio of lithium acetate dihydrate, nickel acetate tetrahydrate, cobalt acetate tetrahydrate and manganese acetate tetrahydrate is 1.3:0.135:0.175:0.495; and an additional 3% molar amount of lithium acetate dihydrate is added to compensate for the lithium loss during the heat treatment process; the total concentration of metal acetate in the precursor solution is 0.18 mol / L, and the concentration of citric acid monohydrate is 0.35 mol / L;

[0064] (2) The precursor solution obtained in step (1) is sent to a spray dryer by a peristaltic pump, and spray dried at high temperature and high pressure, wherein the inlet temperature of the spray dryer is 250° C., the outlet temperature is 113° C., and the feed rate is 2 L / h; then placed in an alumina crucible (120 mm, 120 mm in width, and 50 mm in height), and the alumina crucible is placed in a box furnace, and heated to 1200° C. at a heating rate of 4° C. / min in an air atmosphere, and kept warm for 18 min to complete the heat treatment process, thereby obtaining a lithium-rich manganese oxide positive electrode material;

[0065] (3) placing the lithium-rich manganese oxide positive electrode material obtained in step (2) in a low-pressure radio frequency plasma treatment device, evacuating the quartz tube to a vacuum degree of 0.1 Pa, slowly introducing nitrogen, then slowly increasing the gas flow rate, and ensuring that the air pressure in the quartz tube is stable. After ventilation for 20 minutes, turn on the radio frequency automatic matching device and the radio frequency power supply, maintain a power of 200 W, and discharge for 30 minutes to perform radio frequency plasma treatment to obtain a radio frequency plasma modified lithium-rich manganese oxide positive electrode material.

[0066] Comparative Example 1:

[0067] A lithium-rich manganese oxide positive electrode material, the chemical formula of which is: Li 1.2 Ni 0.132 Co 0.172 Mn 0.492 O2, the preparation method thereof comprises the following steps:

[0068] Excluding step (3), the rest is the same as in Example 1 to obtain a lithium-rich manganese oxide positive electrode material (named LRO).

[0069] Test example

[0070] 1. XRD test

[0071] The lithium-rich manganese-based positive electrode materials prepared in Examples 1-2 and Comparative Example 1 were subjected to XRD tests to test the basic structure of the lithium-rich manganese-based positive electrode materials. The results are shown in Figure 1 .

[0072] Depend on Figure 1It can be seen that after RF plasma treatment, the (003) peaks of LRO / N2-20 min and LRO / N2-30min shifted to the low angle direction, indicating that the c-axis interlayer spacing increased, which is beneficial to lithium ion transmission and greatly improves its rate and cycle performance.

[0073] 2. SEM test

[0074] The lithium-rich manganese-based positive electrode materials prepared in Examples 1-2 and Comparative Example 1 were subjected to SEM tests to test the surface morphology and approximate size of the lithium-rich manganese-based positive electrode materials. The results are shown in Figure 2 .

[0075] Depend on Figure 2 It can be seen that there is no obvious change in the particle morphology before and after RF plasma treatment, and the size is between 200nm and 300nm. This shows that the high-energy particles in RF plasma bombarding the surface of lithium-rich manganese cathode materials will not cause surface morphological defects, nor will they cause severe etching on the surface and destroy the surface structure.

[0076] 3. XPS test

[0077] The lithium-rich manganese-based positive electrode materials prepared in Examples 1-2 and Comparative Example 1 were subjected to XPS tests to test the surface structure of the lithium-rich manganese-based positive electrode materials. The results are shown in Figure 3-5 .

[0078] Depend on Figure 3-5 It can be seen that the oxygen vacancy content of the lithium-rich manganese-based positive electrode materials prepared in the embodiments of the present invention has increased significantly. After 20 minutes and 30 minutes of treatment, the oxygen vacancy content is 30.47% and 34.64%, respectively, which are higher than the oxygen vacancy content of the unmodified lithium-rich manganese material (27.76%). This pre-constructed oxygen vacancy helps to stabilize the lattice oxygen stability of the material surface and inhibit irreversible oxygen precipitation during high-voltage charging. At the same time, the valence state of Mn increases, which plays a role in stabilizing the structure, and the valence state of Ni decreases, which will contribute more capacity.

[0079] 4. Electrochemical performance test

[0080] The lithium-rich manganese-based positive electrode materials prepared in Examples 1-2 and Comparative Example 1 were used to prepare batteries respectively, and then the electrochemical performance was tested. The battery preparation method is as follows:

[0081] 1. Preparation of positive electrode sheet

[0082] The lithium-rich manganese-based positive electrode material and Super P were weighed in a mass ratio of 8:1 and placed in a ball mill, tungsten carbide ball milling beads were added, the ball-to-material mass ratio in the ball mill was 100:1, and alcohol was added as a dispersant. After ball milling for 6 hours, the mixture was dried in a drying oven to obtain a mixture A.

[0083] Weigh 285 mg of mixture A and 1250 mg of 1.2% CMC solution, stir at room temperature for 2 h, ultrasonicate for 2 h, stir again for 2 h, coat on aluminum foil with a 0.15 μm scraper, dry in a vacuum drying oven at 110 ° C for 20 h, cut into electrodes with a diameter of 10 mm, and then transfer the cut electrodes to a vacuum oven at 115 ° C for 10 h for use.

[0084] 2. Assemble CR2025 stainless steel button battery

[0085] Using a metal lithium sheet as the negative electrode, 250 μL of LBC-3045I(G) commercial electrolyte was dripped into the battery. The CR2025 stainless steel button cell was assembled in a glove box filled with argon gas and with a moisture content of less than 0.01 ppm. The charge and discharge performance was tested after standing at 45°C for 40 hours.

[0086] CR2025 stainless steel button battery electrochemical performance test:

[0087] The cycle performance of the prepared battery was tested by constant current charge and discharge. The test temperature was 25°C, the voltage window was 2.0-4.8V, and the current density was 0.1C, 0.2C, 0.5C, 1C, 2C, 5C and 10C, respectively. 1C = 200mA / g. The results are shown in Figure 6-9 .

[0088] Depend on Figure 6 It can be seen that the lithium-ion battery prepared by the lithium-rich manganese oxide positive electrode material LRO / N2-30 min in the present invention has a maximum first discharge specific capacity of 271.89 mAh / g at a current density of 20 mA / g.

[0089] Depend on Figure 7-8 It can be seen that the lithium-ion battery prepared by the lithium-rich manganese oxide positive electrode material LRO / N2-30 min in the present invention has an initial discharge specific capacity of 271.89 mAh / g at a current density of 20 mA / g. After 325 cycles at a current density of 200 mA / g, the capacity retention rate is as high as 70%. After 400 cycles, the capacity retention rate is as high as 63.59%. This is mainly because the increase in interlayer spacing leads to rapid transmission of lithium ions, and the increase in oxygen vacancy content inhibits lattice oxygen release and enhances electron / ion transport, thereby improving cycle stability. The lithium-ion battery prepared by the lithium-rich manganese oxide positive electrode material LRO / N2-30 min in the present invention maintains excellent performance in the rate performance tests of 0.1C, 0.2C, 0.5C, 1C, 2C, 5C and 10C.

[0090] Depend on Fig. 9It can be seen that due to the increase of surface oxygen vacancy defects after RF plasma treatment, the c-axis interlayer spacing increases, thereby promoting the transport of lithium ions and electrons, so that the lithium-ion batteries prepared by LRO / N2-20 min and LRO / N2-30 min using the lithium-rich manganese oxide positive electrode material in the present invention have a capacity of 144.24mAh / g and 169.28mAh / g at a current density of 1000mA / g, which is higher than the capacity of LRO without plasma modification (131.37mAh / g). At this current density, after 285 cycles, the capacity retention rate is as high as 70%, showing excellent rate performance and cycle stability.

[0091] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a radio frequency plasma modified lithium-rich manganese oxide positive electrode material, characterized in that: The following steps are involved: (1) lithium acetate dihydrate, nickel acetate tetrahydrate, cobalt acetate tetrahydrate, manganese acetate tetrahydrate and citric acid monohydrate are mixed, added into deionized water, and stirred to prepare a precursor solution; (2) spray drying the precursor solution obtained in step (1), and then heat treating it to obtain a lithium-rich manganese oxide positive electrode material; (3) Subjecting the lithium-rich manganese oxide positive electrode material obtained in step (2) to radio frequency plasma treatment to obtain radio frequency plasma modified lithium-rich manganese oxide positive electrode material.

2. The method for preparing the radio frequency plasma modified lithium-rich manganese oxide positive electrode material according to claim 1, characterized in that: In step (1), the molar ratio of lithium acetate dihydrate, nickel acetate tetrahydrate, cobalt acetate tetrahydrate and manganese acetate tetrahydrate is 1.1-1.3:0.13-0.135:0.17-0.175:0.49-0.

495.

3. The method for preparing the radio frequency plasma modified lithium-rich manganese oxide positive electrode material according to claim 1, characterized in that: The total concentration of metal acetate in the precursor solution is 0.13-0.18 mol / L, and the concentration of citric acid monohydrate is 0.25-0.35 mol / L.

4. The method for preparing a radio frequency plasma modified lithium-rich manganese oxide positive electrode material according to claim 1, characterized in that: In step (2), the inlet temperature of the spray drying is 200-250°C, the outlet temperature is 110-115°C, and the feed rate is 1-2L / h.

5. The method for preparing a radio frequency plasma modified lithium-rich manganese oxide positive electrode material according to claim 1, characterized in that: In step (2), the temperature is raised to 900-1200° C. at a heating rate of 2-4° C. / min in an air atmosphere and kept at that temperature for 18-22 minutes to complete the heat treatment process.

6. The method for preparing a radio frequency plasma modified lithium-rich manganese oxide positive electrode material according to claim 1, characterized in that: In step (3), the lithium-rich manganese oxide positive electrode material obtained in step (2) is placed in a radio frequency plasma treatment device, the quartz tube is evacuated to a vacuum degree of 0.1 Pa, nitrogen is introduced, and then the gas flow rate is increased and the gas pressure in the quartz tube is ensured to be stable. After ventilation for 10 minutes, the radio frequency automatic matcher and the radio frequency power supply are turned on to perform radio frequency plasma treatment.

7. The method for preparing a radio frequency plasma modified lithium-rich manganese oxide positive electrode material according to claim 1, characterized in that: In step (3), the radio frequency plasma treatment power is 200W and the time is 1-30min.

8. The radio frequency plasma modified lithium-rich manganese oxide positive electrode material obtained by the preparation method of the radio frequency plasma modified lithium-rich manganese oxide positive electrode material according to any one of claims 1 to 7.

9. The radio frequency plasma modified lithium-rich manganese oxide positive electrode material according to claim 8, characterized in that: Its chemical formula is Li 1.2 Ni 0.132 Co 0.172 Mn 0.492 O2.

10. Use of the radio frequency plasma modified lithium-rich manganese oxide positive electrode material according to claim 8 or 9 in the preparation of lithium-ion batteries.

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